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Floods in German June 2013Post-flood field investigation, July 2& 3, 2013
Preliminary Findings
Bas Jonkman, Timo Schweckendiek, Guy Dupuits (TU Delft); Torsten Heyer (TU Dresden); Joop de Bijl (STOWA); Astrid Labrujere (RWS)
in collaborationwith:
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Ob ectives and sco e
• Post-flood field investigation July 2 & 3
• Focus on dike breaches and flood fighting• eam:
• Torsten Heyer (TU Dresden)
• Bas Jonkman (TU Delft, Rijkswaterstaat, ENW)
•
Timo Schweckendiek (TU Delft, Deltares, ENW)• Joop de Bijl (STOWA, Waterschap Aa en Maas)
• Gu Du uits TU Delft
• Astrid Labrujere (Rijkswaterstaat)
•
July 2, Reinhard Pohl (TU Dresden)• ,
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Preci itation and Floods
NOS
NRC 6 June 2013
• Large flood event:• –
depending on location / river• At some places larger than 2002
flood event
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Affected areas
Havel -> Elbe
Wittenberge
ElbeSaale
Magdeburg (Elbe)
Fischbeck / Tangermünde (Elbe)
Mulde AueHavelElster
Saale -> Elbe
Dresden (Elbe)
Passau (Donau)
Donau
er e ue
IsarInn
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Overview of investi ated sites
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Dresden overview
Bypass
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Dresden facts and fi ures
• 2002 flood event:
• +9.40 meter water level in the Elbe (1/200 per year event),m on euro n amage
• The Weißeritz river, a tributary river to the Elbe, had a 1/500
per year event
• Various measures were taken after this event: floodgates,mobile flood protection, improvement of hydraulic roughness,
increasin rotection to at least 1 100 er ear
• 2013: +8.77 m water level Elbe (1/50 per year event)
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Dresden im ressions
2013 - Picture taken by Reinhard Pohl
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Dresden - im ressions
2013 - Picture taken by Reinhard Pohl
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Dresden flood ates
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Dresden flood ates
Gate lower
than floodwallo a ow
overflow
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Dresden erosion
unexpected erosion next to the Marienbrücke in
the bypass (after removing obstacles downstream)
front
back
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Bitterfeld - situation
• Coal mining, leaving pits of 60 meters deep
•
Mining activities have stopped• urne n o a recrea ona area w s pp ng ar our
• Concentration of chemical industry in the area
• City of Bitterfeld
•
On the border between Sachsen en Sachsen-Anhalt• Thousands of people were evacuated because of threat from
lakes
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Bitterfeld re-breach situation
Seehausener See
o zsc esee
Mulde
© Jens Wolf/dpa
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Flood flow direction
Flood flow direction
Goitzschesee(lower water level) 1. Breach in river dike
2. Overland
∆ Hnormal = 3m ∆ Hflood = 9m
pumpsMuldecanal
Seehausener See
flow,breaching of
road
breach
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1. Bitterfeld – Mulde breach
• Breach on the Mulde river, one of
multiple breaches
• 25 m wide breach, relatively high on
slope
• Wells on the inside of sandy material,
possibility of piping mechanismBreach (filled)
pondstructure
Context:
• ext to sma ewater ng structure an
small pond
• In 2002 a breach occurred in the samearea, a few hundred meters upstream
from the current breach.
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2. Bitterfeld - Breaches in Road Nr. S12
• Large breach in road (200m or more)
• ver opp ng an eros on o roa an e pa
Flood flow direction
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3. Bitterfeld, Breaches in Channel
embankments between lakes
• Seelhausener Lake fills due to breach (several meters)
• Overflow and breaching of adjacent canal dikes• nsuccess u a emp o c ose reac es w g ags y e cop ers
• Cascading effects to Grosse Goitscherzee, threatening city of
Bitterfeld
Flood flow direction
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Bitterfeld dewaterin
• Breaches created with dynamite for dewatering
Flooded /lake side
river
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Breitenha en - levee breach
River
flooded
DPA / Salzlandkreis
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Breitenha en - inner slo e failure
Reuters
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Breitenha en
• Located on Saale river, water levels about 1~1.5m below crest
• Trees located in front of dike
• Dikes consisted of clay, slope about 1:2.5 to 1:3
,
• Part of the dike remained for 10 hrs, then breached
• 150m breach
• e re n orcemen p an was ava a e, u no ye mp emen e
• Emergency measures:
• First round of bigbags delivered by helicopters
• After that no army assistance available anymore
• For dewatering:
•
• Breach opened by equipment for dewatering
• Pumps installed to dewater the urban area
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Fischbeck levee breach
River Elbe
Foto: REUTERS/Thomas Peter
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Fischbeck dike breach - eneral
• breach location located at “corner”
• Western side of the Elbe,• wa er eve e ow cres . m ~ . m
• dike: about 5m high, moderate/steep slope (about 1:3?), no
berm
• dike body: clayey sand (sandy clay in lower part)
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Fischbeck dike breach
Failure process (according to eye witnesses)
, -
• heavy flood fighting to prevent breach (sand bags, big packs)
• breach occurred around midnight (Sunday 9 June around00:01 AM)
• inner slope sliding/breach occurred fast (10 ~ 20s)
• initial width 50m rowth to 100m within hours 2-3m dee
scour hole• estimated inflow up to 700-1000 m3 /s (different figures in
• Water was within town of Fischbeck (~ 2km) within 5
minutes• Fisc ec a een evacuate previous y
• flooding extended in a wide area (up to the Havel river, tens
of km
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Fischbeck - ost-breach
modified after dpa photo
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riverbarges
breach
Temporarydike &sheetpile
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Fischbeck breach emer enc
repairs
• Three barges sunk in front of the
breach using explosives• n ow re uce s gn can y
• breach finally closed when water was
levelled out
• Temporary flood defence:
• Sheet pile in the breach (8 ~ 11m)
• Earthen dike roadwa in front
• Ships are being removed, new dike
will follow different alignment
dpa / dpa
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Fischbeck breach emer enc re airs
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Fischbeck emer enc re air
Source: MDR Sac sen-An a t
VIDEO
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Fischbeck - local instabilit
• Few hundred meter from breach site
• Seems initiation of slip circle over about 25 ~ 30m
• Sheet pile in dike and bigbags on slope implemented as
emer enc measures
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Concludin remarks
• Large flood event:
• Return period 50 – 500 year depending on location / river
• At some places larger than 2002 flood event
• Water levels mostl close to the crest of dikes no overflow • Several dike failures
• Visited failures were due to geotechnical mechanisms at
• Instability at Fischbeck and Breitenhagen• Possibly piping at Bitterfeld river dike breach, and overflow for
canal and road breaches
• Complex system / cascading effects at Bitterfeld
• Dike failure -> road breachin -> lake fills -> canal dikes fail ->Second lake fills up, threatens town of Bitterfeld
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Recommendations
• Anal ze and hindcast dike failures data collection stabilit
and piping analysis)
• Large reliance on emergency measures
•
• During inflow breaches could not be closed by bigbags or barges
Recommended to evaluate performance of emergency
measures
• Evaluate evacuations and emergency response
• Further anal sis of other to ics:
• Hydrological system performance (incl. cascades and retention)
• Damage
- • For the Netherlands:
• Pay attention to dewatering and breach closure plans
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Acknowled ements
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